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Dec 10, 2020 | 06:47 PM

UncleBuck18

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No heat

I have a 2001 F150 with the 4.6 engine. I replaced the thermostat and the blend door IS working properly, and I flushed the heater core and I still have no heat. What else could this be?

Dec 10, 2020 | 07:21 PM

projectSHO89

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Did you check for hot coolant flow through the heater core?

Dec 10, 2020 | 07:39 PM

UncleBuck18

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Yeah, they both get hot over time

Dec 10, 2020 | 07:42 PM

projectSHO89

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How hot over how much time?

Dec 10, 2020 | 08:02 PM

bbsitum

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Heat **** cracked or worn out. I slid piece of aluminum in and work since. I always tough people check that first.

Dec 11, 2020 | 09:59 AM

alloro

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Quote:

Originally Posted by UncleBuck18

Yeah, they both get hot over time

Once the engine is up to full temperature those hoses should be too hot to hold. If you can hold onto them they're not hot enough.

Dec 11, 2020 | 10:51 AM

UncleBuck18

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Between 10-15 minutes the inlet and outlet hose gets very hot to the touch, and I’ve noticed when I drive with both heat and air off and I turn it on heat it will blow a rush off hot air but then it gets back cold

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Dec 11, 2020 | 01:05 PM

UncleBuck18

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Coolant looks like a nice lime green

Dec 11, 2020 | 01:10 PM

#10

projectSHO89

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Quote:

and I’ve noticed when I drive with both heat and air off and I turn it on heat it will blow a rush off hot air but then it gets back cold

At that point and with the blower still on high, check the temperature of the hoses.

Your basic symptom is of insufficient hot coolant in or passing through the core. Turning off the blower allows it to accumulate in the core and plenum. You need to determine whether or not here is a very substantial drop in the temperature of the outlet.

Dec 11, 2020 | 05:27 PM

#11

UncleBuck18

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So should I try flushing the heater core back out again? If the temp on the outlet hose decreases after the rush of hot air?

Dec 12, 2020 | 07:08 AM

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formerjeepguy

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Quote:

Originally Posted by UncleBuck18

So should I try flushing the heater core back out again? If the temp on the outlet hose decreases after the rush of hot air?

you can try, but if your water pump isn't working right you won't get enough coolant flow through the heater core.

Dec 13, 2020 | 10:01 AM

#13

alloro

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Quote:

Originally Posted by UncleBuck18

So should I try flushing the heater core back out again? If the temp on the outlet hose decreases after the rush of hot air?

Like projectSHO89 said above, you need to feel the hoses again after the initial blast of heat goes away and the air gets cool again. If one hose is hot and the other cold you have a blockage in the heater core. If both are hot you have a blend door issue or scale build-up on the inside of the heater core.